Corn processing hits new speeds with hydraulics

A staff report

Sun, 1997-06-01 (All day)

You might think there wasn’t much to improve on in the corn production area of food processing — after all, the last patent for a corn cutter was applied for in 1950. However, Ron Anderson and Tom Kessler, co-founders of A&K Development Co., Eugene, Oreg., had plenty of ideas when they formed their company. Both had prior experience in the food processing industry, and quite a few ideas of how they could incorporate fluid power into a new generation of corn processing equipment. With the assistance of John Hughey of Spencer Fluid Power in Eugene, Oreg., their fluid power distributor, they put those plans into action.

Figure 1 — Lines of orienters and dekerneling machines dominate this view of a food plant in Minnesota. By using hydraulics extensively in the designs of their machines, A&K Development Co. has build a series of corn processing machines that can remove kernels from over 100 cobs of corn per minute.

Processing the corn
After being harvested in the field, corn is brought to the food processing plant, Figure 1, and dumped down a chute to the corn huskers. As corn slides down the face of the husker, dozens of rubberized rollers rip the husk away from the ear. By the time the ears reach the bottom of the husker, they are devoid of any husk, and are ready for the next step in production.

Figure 2 — Eaton’s Series J hydraulic motor is used on both the corn orienter and the corn dekerneler. The motors are rated at 5.5 gpm continuous, with a peak torque of 733 in.-lb and a working pressure of 2175 psi intermittent. Rated speed is 650 rpm at continuous flow

Conveyors then carry the ears to an orienting machine, which performs three functions: singulation, positioning, and orienting. A series of angled thin plates, referred to as a shuttle flow, oscillate up and down. As these plates move, individual ears of corn are stepped up from one plate to the next, successively guiding the ears higher and higher. When the ear reaches the top of the orienter, it is allowed to fall down to another conveyor located behind the orienter. However, a strategically placed friction plate catches the fatter end of the ear as it falls, tipping the pointed end downward, so that it touches the conveyor first. The forward movement of the conveyor pulls the ear from the friction plate, ensuring that the pointed end of the ear will face the cutting head.

A&K chose four J2 series hydraulic motors from Eaton Hydraulics, Eden Prairie, Minn, Figure 2, to move, singulate, and orient the corn. These particular motors were chosen because of their high power density, and their ability to be kept in synchronization — a key part of the design of the orienter.

The hydraulically powered orienter has a higher efficiency than competitive models, with a resulting tipfirst orientation of greater than 90%. All of the motors are run by an Eaton Series 26 pump, Figure 3, in a tandem configuration.

A new way of dekerneling
The most impressive application for hydraulics in this process is on the dekerneler — the device that grabs and then surgically removes the kernels of corn from the ear.

Figure 3 — Eaton Series 26 high-pressure gear pump power the motors on the orienter. The pumps have a rated speed of over 3000 rpm, with a maximum continuous pressure of 3000 psi and a displacement of 1.87 in.3/rev.

Although no major design changes had been made to the machine in over 40 years, there was one big problem inherent to the design that both Anderson and Kessler were determined to overcome.

First, a little background: the dekerneler’s main feature is a series of six hourglass rolls, which are arranged in three parallel pairs. Corn is fed, via the first four rolls, to a dilating aperture cutting head (which opens and closes like a camera iris). As the ear of corn passes through, the cutter blade cuts the kernels from the cob. Then the final two hourglass rolls pull the spent cob from the machine.

A large fixed gearbox and six universal joints transfer torque to each of the six rolls and the cutter. When a cob jams in the cutter, sensors instruct the machine to instantly reverse — not a particularly big deal, until you consider that in an average processing season, this happens some 20 million times. As one might expect, this causes considerable stress and wear on the brass gears and the universal joints; as a result, both have to be serviced and replaced quite frequently — at least once per season.

A&K decided that it would be a tremendous advantage to use hydraulic motors in place of bulky electric motorss gearboxes. Hydraulics had already proven itself in other equally harsh areas of food processing. They chose the same series of hydraulic motors as used on the orienter, using a single motor to drive each of the six shafts (a seventh motor drives the cutter itself), Figure 4. The seven motors are connected in series, to keep their speeds closely matched — otherwise, the cobs would be torn up. The particular model of motor used here has a displacement of 0.79 in.3/rev, compared with 1.93 in.3/rev on the orienter.

One major benefit of the old way of doing things was that the universal joints provided a degree of flexibility — this was beneficial because it allowed for varying dimensions of the corn cob. In order to eliminate the need for the joints, Eaton provided A&K with a special spline on the motor output shaft that allows for a strong coupling with the working shaft. Then, A&K designed a patented motor mount that allow the entire motor and shaft to flex according to the diameter and curvature of each cob.

Call it a success
Now, when a cob sticks or breaks off in the cutter head, a sensor instructs the programmable controller to simply reverse the hydraulics. With the hydraulic system in operation on the machine, there were no problems with the first full-fledged model in 1996, and none are expected in the future.

Figure 4 — Six Eaton J Series hydraulic motors are plumbed in series, above, to control the six rotating hourglass rolls, below, that guide the individual ears of corn into the machine. Cobs enter from the right side, and encounter a cutting head (not shown) after a second set of rolls. A third set of rolls pulls the spent cob through, to a conveyor that carries them away.

Perhaps the most amazing part of this story was the simulated test that A&K performed on the first working prototype of the machine. In the simulation, which was far more abusive and aggressive than would be found in real life situations, the machine went through 20 million cycles without a single problem. Kessler admits that he doesn’t know what the machine’s lifetime is. “At that time [after 20 million cycles], we said, ‘Let’s build it,’ because it was the equivalent of three processing seasons. So, we’re boasting that we have three to five seasons; but we may have more than that before any maintenance would be required.”

One unexpected side benefit of the hydraulics is improved speed. The A&K corn cutter can dekernal between 100 and 115 cobs per minute (100,000 to 115,000 lb/day), with a case yield greater than that provided by competitive units. Thanks to their innovative design, A&K now holds a major part of the business of food processing plants in more than 25 countries all over the world. And they will surely be thinking of new hydraulic applications before another 47 years pass on by.